Symptoms of anxiety add significant burden to many autistic individuals and their loved ones. There is an urgent need for better understanding of the unique underlying mechanisms of anxiety in ASD, and for the development of more specific assessment methods and treatment recommendations. This special issue brings together 24 articles grouped into three themes; mechanisms, measurement, and intervention. The result is a review of current anxiety research in ASD that is both broad and deep. Key themes include recognition of the importance individual differences in aetiology and presentation of anxiety in ASD, the need for a more nuanced understanding of the interactions between anxiety and characteristics of ASD and the need to develop appropriately adapted treatments.